Systematic coarse-graining in nucleation theory

Abstract

In this work we show that the standard method to obtain nucleation rate-predictions with the aid of atomistic Monte-Carlo simulations leads to nucleation rate predictions that deviate 3 − 5 orders of magnitude from the recent brute-force molecular dynamics simulations [J. Diemand, R. Angélil, K. K. Tanaka, and H. Tanaka, J. Chem. Phys. 139, 074309 (2013)] conducted in the experimental accessible supersaturation regime for Lennard-Jones argon. We argue that this is due to the truncated state space literature mostly relies on, where the number of atoms in a nucleus is considered the only relevant order parameter. We here formulate the nonequilibrium statistical mechanics of nucleation in an extended state space, where the internal energy and momentum of the nuclei is additionally incorporated. We show that the extended model explains the lack in agreement between the molecular dynamics simulations by Diemand et al. and the truncated state space. We demonstrate additional benefits of using the extended state space; in particular, the definition of a nucleus temperature arrises very naturally and can be shown without further approximation to obey the fluctuation law of McGraw and Laviolette. In addition, we illustrate that our theory conveniently allows to extend existing theories to richer sets of order parameters.

Nucleation and droplet growth from supersaturated vapor at temperatures below the triple point temperature

“…The supersaturation S = 73 for T QES = 0.50 is higher than the supersaturations in experiments of nucleation in Argon [7], and it is much higher than in a supercooled gas in nature. The released latent heat dissipates into the surrounding and establish a temperature gradient between the growing droplet and the gas.…”

“…Realistic computer simulations of nucleation require very big systems of many particles and simulated over long times. But the actual supersaturations are even for these systems typically significant higher than what appears in nature [7]. Most simulations are performed by Molecular Dynamics (MD) simulations, and for systems of Lennard-Jones (LJ) particles and with comparison of nucleation rates with corresponding rates obtained for supersaturated Argon gas [8].…”